1. Field of the Invention
The present invention relates to a substrate drying device, drying method and substrate dried by the method, and more particularly, to a substrate drying device for drying various kinds of application materials, such as a solder resist material, applied to a surface of the substrate before a subsequent step when printed circuit boards are fabricated, and drying method and substrate dried by the method.
2. Background Art
FIG. 4 shows an example of a conventional substrate drying device of this kind in the prior art. Substrates 10 on which an application material 11 such as a solder resist material is applied in filmy state are placed on an appropriate transport means, such as a belt conveyor 91, at regular interval. The belt conveyor 91 is provided with a cover 92 which covers the belt conveyor 91 like a tunnel, and plural heating means 93, such as a heater, are provided within the cover 92. Drying is achieved by heating the substrates 10 passing through inside of the cover 92 using these heating means to accelerate vaporization of a solvent in the application material 11.
Drying of the application material 11 is performed by evaporating the solvent in the application material 11 in order to prevent generation of some trouble in subsequent steps, such as an exposure step. In addition, generation of a defect in a development step or the like should be prevented by eliminating air bubbles which are involved into the application material 11 during applying operation.
However, in the substrate drying device 90 having a configuration of the prior art, compatibility between reducing the drying time and eliminating air bubbles in the application material 11 was difficult. In other words, if the heaters 93 increase a heating temperature to accelerate vaporization of a solvent, the application material 11 will be dried rapidly to increase its viscosity, resulting in difficulty in eliminating air bubbles.
In such a case, generation of defective in the following steps is often originated from the air bubbles in the application material 11. Therefore, an effect resulted from only reducing the drying time in order to decrease a proportion defective can not be expected, so that the time required to dry the substrates 10 in the substrate drying device 90 will need a long period of time, such as 10 to 20 minutes.
This causes a detention time in a step to increase, resulting in problems of detracting a productivity and the like, and also this needs a long period of detention time as described above in a consecutive production steps of the substrates 10, resulting in an increase in the size of the substrate drying device 90 itself. Thus, such a problem that an arrangement of the substrate drying device 90 becomes difficult may occur, accordingly, a need arises for solving these problems.
Additionally, even if extended periods are used for the method described above, eliminating air bubbles can not be improved. That is, the substrates 10 are sometimes dried with air bubbles more than 30 micrometers involved, so that defective substrates may be finally produced.